1. Field of the Invention
The present invention relates to a fabrication method for a functional surface that has self-cleaning ability and superhydrophilic or super water-repellent anti-reflective property; and, more particularly, to a fabrication method for a functional surface that has anti-reflective property which is less than 5% of a reflectivity of a transparent substrate, self-cleaning ability by which organic contaminants on the substrate surface are decomposed by themselves and superhydrophilic property, and a fabrication method of a functional surface that has anti-reflective property which is less than 5% of a reflectivity of a transparent substrate, super water-repellent property with self-cleaning ability due to its hydrophobic property.
2. Description of Related Art
In recent, studies for engineering utilization inspired from natural nanostructures are actively in progress. Representative examples are a lotus leaf that is super water-repellent and a moth eye that is non-reflective.
In general, the non-reflection is a concept of anti-reflection, and an anti-reflective surface technology is a technology that reduces reflection of light caused by rapid change in refractive index on a surface of an optical device to increase the amount of light transmitting through the optical device.
A representative model of the non-reflection is a moth eye: since the moth eye is formed of well arranged nanostructure and is thus very low in light reflection, the moth is able to protect itself from predators such as birds and is also able to secure sight, which allows easy activity, with less light even at night.
The non-reflective, i.e. anti-reflective surface using this nanostructure is applied to monitor including OLED/LCD, lighting or advertizing including LED, solar cell, glass for industrial or home appliance including instrument panel for vehicle, optical lens for camera and so on, and can reduce glare due to reflection of external light and reduce the amount of light emerged from the inside to thereby provide clear and bright images.
In general, the anti-reflective surface is made by coating chemicals having a refractive index, which is between those of air and substrate, as a thin film using electron beam deposition or ion assisted deposition. Also, it is necessary to deposit different materials of various layers with different refractive indexes if anti-reflection at different wavelengths is required.
However, the anti-reflective surface using nanostructures has an advantage that it shows anti-reflective effect in wide angle of incidence and wavelength range compared to the existing technology using the coated thin film.
The anti-reflective surface using nanostructures is approached in various nanoprocesses. In recent, there has been reported fabrication of a nanostructure on a silicon surface through dry etching using nanosphere lithography and SF4 plasma, and anti-reflection effect thereof (Peng Jiang et al. APL, vol. 92, 061112, 2008). However, in the aforementioned study, silica nanospheres are arranged on silicon in a single layer and an uneven structure is then formed on the silicon surface using plasma, and the product has a problem that it is not transparent.
Further, the same study group reportedly made a mold using silica nanoparticles and reproduced it with polydimethylsiloxane (PDMS) to synthesize a structure of polyethoxylated trimethylolpropane triacrylate (PETPTA) on glass by UV polymerization (Peng Jiang et al. APL, vol. 91, 101108, 2007). However, there are problems that it is difficult to adjust the shape of the structure and durability is weak.
In general, since the surface of vehicle glass or window pane for building has a low angle of contact for water between 20° and 40°, water droplets are attached to and grow on the surface and then flow down in a shape of heterogeneous water curtain upon the rain. This heterogeneous water curtain causes light scattering to disturb driver's sight especially upon the rain or at night in the case of the vehicle glass, and easily contaminates the surface together with dust or yellow dust in the case of the window pane for building. Meanwhile, in a high rise building which is difficult to clean and has a large area, a self-cleanable glass on which organic/inorganic substances are removed by themselves has a significant advantage in maintenance of the building.
In consideration of above description, the present invention aims to provide a fabrication method for a functional surface, which allows large area treatment, easy fabrication in short time and self-cleaning of organic/inorganic contaminants, and has uniform and deterioration-restricted anti-reflective property, and superhydrophilic property or super water-repellent property showing a self-cleaning ability.